The Mediterranean Sea hosts numerous jellyfish species, gelatinous creatures with umbrella-shaped bodies and trailing tentacles found throughout the basin. Some species are native, others introduced, contributing to varied forms. They are common, particularly during warmer months, for those visiting the region’s coasts.
Key Mediterranean Jellyfish Species
Distinct jellyfish species inhabit the Mediterranean, each with unique characteristics.
Pelagia noctiluca, known as the mauve stinger or purple jellyfish, is frequently encountered. It has a bell-shaped body, typically 3 to 12 centimeters in diameter, with long, thin tentacles extending up to 2 meters. Its color shifts from orange-brown in adolescence to purple or pink in adulthood, with warts on its upper surface. It is particularly prevalent in the western and central Mediterranean, Aegean, Ionian, and Adriatic seas.
Rhizostoma pulmo, also known as the barrel or dustbin lid jellyfish, is another common inhabitant. Reaching up to 1 meter in bell diameter, it has a dome-shaped bell with long, flaring mouth arms and short, pointed tentacles. Its coloration varies from pale pink to orange-brown. While generally harmless, contact can lead to dermatitis and ulcers.
Cotylorhiza tuberculata, or fried egg jellyfish, is widespread in the Mediterranean. It is recognizable by its flattened, yellowish-brown mushroom-shaped bell with a large central, dark orange protuberance. It has short, powerful tentacles with button-shaped, white or blue appendages. It often forms large colonies near fishing grounds or tourist beaches.
Aurelia aurita, the moon jellyfish, is another translucent species commonly found in the Mediterranean. It has a saucer-shaped, translucent body with short tentacles and four horseshoe-shaped reproductive organs (white or violet). Its color ranges from white to pale blue. Chrysaora hysoscella, the compass jellyfish, is less common but encountered periodically. It has an umbrella shape with a clear bell and radiating brown lines, resembling a compass face. Its body can measure up to 30 cm, tentacles can reach 5 meters.
Understanding Jellyfish Stings
Jellyfish stings occur when specialized stinging cells (nematocysts) on their tentacles release venom. The venom, a neurotoxin, is injected into the skin, causing symptoms. Severity varies by jellyfish species, venom amount, and individual sensitivity.
Common symptoms include immediate pain, burning, redness, and swelling at the contact site. Tentacle marks may also appear on the skin. Itching, throbbing, or muscle cramps can also occur. While most stings result in moderate localized reactions, severe symptoms like widespread swelling, difficulty breathing, chest pain, heart palpitations, nausea, vomiting, or fainting require immediate medical attention.
For immediate first aid, carefully remove visible tentacles with tweezers or a plastic card, avoiding direct contact. Do not rub the affected area; this can cause more venom to be released. Rinse the sting with seawater, then wash with fresh water for a few minutes.
Applying a baking soda slurry (50% baking soda, 50% seawater) for five minutes helps prevent further venom discharge from unfired stinging cells. Soaking the affected skin in hot water (43-45°C / 110-113°F) for 20 to 45 minutes can alleviate pain.
A mild hydrocortisone cream or oral antihistamine can reduce itching and swelling. Avoid using urine, alcohol, or fresh water directly on certain stings, as these can worsen the reaction.
Jellyfish in the Mediterranean Ecosystem
Jellyfish act as predators and prey in the Mediterranean food web. They feed primarily on small marine organisms like plankton, fish eggs, and larvae. Some species are voracious carnivores, consuming crustaceans and other jellyfish. Large jellyfish populations can exert significant predation pressure on ichthyoplankton and crustacean plankton, food sources for commercially important fish species.
Mediterranean jellyfish populations are increasing due to several factors. Rising water temperatures contribute to jellyfish expansion and abundance. Warmer waters can trigger jellyfish to emerge from their juvenile polyp stage.
Overfishing of species that prey on jellyfish or compete for food increases jellyfish numbers. A decrease in large fish, for example, can release jellyfish from competition for food sources like plankton. Human activities like coastal development, nutrient loading, and bottom-trawling are suggested drivers of increased jellyfish abundance.